David Shukman has been to Greenland to look at algae:
Scientists are “very worried” that the melting of the Greenland ice sheet could accelerate and raise sea levels more than expected.
They say warmer conditions are encouraging algae to grow and darken the surface.
Dark ice absorbs more solar radiation than clean white ice so warms up and melts more rapidly.
Currently the Greenland ice sheet is adding up to 1mm a year to the rise in the global average level of the oceans.
It is the largest mass of ice in the northern hemisphere covering an area about seven times the size of the United Kingdom and reaching up to 3km (2 miles) in thickness.
This means that the average sea level would rise around the world by about seven metres, more than 20ft, if it all melted.
That is why Greenland, though remote, is a focus of research which has direct relevance to major coastal cities as far apart as Miami, London and Shanghai and low-lying areas in Bangladesh and parts of Britain.
Algae were first observed on the Greenland ice sheet more than a century ago but until recently its potential impact was ignored. Only in the last few years have researchers started to explore how the microscopically small plants could affect future melting.
A five-year UK research project known as Black and Bloom is under way to investigate the different species of algae and how they might spread, and then to use this knowledge to improve computer projections of future sea level rise.
The possibility of biologically inspired melting was not included in the estimates for sea level rise published by the UN’s climate panel, the IPCC, in its latest report in 2013.
That study said the worst-case scenario was a rise of 98cm by the end of the century.
Meanwhile, another factor that may be driving the melting has been identified by an Austrian member of the team, Stefan Hofer, a PhD student at Bristol.
In a paper recently published in Science Advances, he analysed satellite imagery and found that over the past 20 years there has been a 15% decrease in cloud cover over Greenland in the summer months.
“It was definitely a ‘wow’ moment,” he told me.
Although temperature is an obvious driver of melting, the paper estimated that two-thirds of additional melting, above the long-term average, was attributable to clearer skies.
What is not known is how this might affect the algae. Their darker pigments are believed to be a protection from ultra violet light – so more sunshine might encourage that process of darkening or prove to be damaging to them.
If ever there was a non-story!
For a start, algae were observed over a century ago. No doubt it has been there for millennia. Why it should make any difference now is anybody’s guess.
And they are not even sure whether more sunshine will make them grow or kill them!
The Black and Bloom project, which Shukman has been visiting, is based near to Kangerlussuaq, in SW Greenland.
Contrary to popular myth, propagated by the likes of Shukman, temperatures in that part of the world are no higher than they were in the 1930s and 40s.
Ilulissat (Station 4221) has a long temperature record, and is very close to Kangerlussuaq:
DMI also concocted a merged SW Greenland series, which shows a similar pattern. 2010 was an anomalously warm year, but no other year since 2000 has exceeded some of those earlier years prior to 1950.
To put matters further into perspective, recent studies have shown that shown that Greenland’s ice sheet actually gained mass between 1961 – 1990:
And for a longer perspective, we have the ice core data.
For some reason, algae did not cause the Greenland ice cap to melt away in all of those earlier warm periods.
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